Publishing options

Several options are available that control the way messages are published.

Withholding reply-to information from subscribers

If we do not want subscribers to be able to reply to publications they receive, it is possible to withhold information in the ReplyToQ and ReplyToQmgr fields of the MQMD by using the MQPMO_SUPPRESS_REPLYTO put-message option. If this option is used, the queue manager removes that information from the MQMD when it receives the publication before forwarding it to any subscribers.

This option cannot be used in combination with a report option that needs a ReplyToQ, if this is attempted the call with fail with MQRC_MISSING_REPLY_TO_Q.

Publication level

Using publication levels is a way of controlling which subscribers receive the publication. The publication level denotes the level of subscription targeted by the publication. Only subscriptions with the highest subscription level less than or equal to the publication's publication level, will receive the publication. This value must be in the range zero to nine; zero is the lowest publication level. The initial value of this field is 9. One of the uses of publication and subscription levels is to intercept publications.

Check if a publication is not delivered to any subscribers

To check if a publication has not been delivered to any subscribers, use the MQPMO_WARN_IF_NO_SUBS_MATCHED put-message option with the MQPUT call. If a completion code of MQCC_WARNING and a reason code MQRC_NO_SUBS_MATCHED are returned by the put operation, the publication was not delivered to any subscriptions. If the MQPMO_RETAIN option is specified on the put operation, the message is retained and delivered to any subsequently defined matching subscription. In a distributed publish/subscribe system, the MQRC_NO_SUBS_MATCHED reason code is returned only if there are no proxy subscriptions registered for the topic on the queue manager.

Parent topic: Writing publish/subscribe applications